The present invention relates to a fixing device for use in an image forming apparatus such as a copying machine, a printer or a facsimile.
Conventionally, there has been a fixing device including a pivotable fixing roller, an endless belt, a first pressure pad, a second pressure pad, and a low friction sheet, wherein the endless belt moves while forming a nip portion in pressure contact with the fixing roller, wherein the first and second pressure pads are placed inside the endless belt and bring the endless belt in pressure contact with the fixing roller at the nip portion, and wherein the low friction sheet is provided between the endless belt and the first and second pressure pads (JP 2005-148618A).
However, the first and second pressure pads have a construction in which the first and second pressure pads utilize the identical low friction sheet in the conventional fixing device. Therefore, the independent actions of the first and second pressure pads are obstructed by the low friction sheet. As the result, there has been such a problem as to fail in maintaining the nip portion to proper nip width and nip pressure. Thus, there have been problems in fixability and conveyability of a recording material at the nip portion since the nip portion has an inferior stability as stated above.
It is often the case where the nip portion cannot be maintained in the proper state particularly after removing the recording material jammed between the fixing roller and the endless belt (after jam treatment of the recording material) or after changing a pressure contact force between the fixing roller and the endless belt (after fixing mode change). This has been a problem to be necessarily solved in developing a fixing device that requires the diversity of the recording material and the reliability of the print quality.